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SpaceWire RMAP Protocol

SpaceWire Working Group Meeting

Steve ParkesUniversity of Dundee

RMAP Review

• Final review before ECSS• Changes since last meeting/draft C• Go through book section by section• Review suggestions for changes from Torborn Holt• Demonstration of RMAP

Changes from Draft C to D• Command descriptions split into:

– Logical addressing– Path addressing– Simplifies overall description

• Error code 12 added in section 6.6 to cover detection of invaliddestination address.

• Multiple error handling:– Order of checking for errors– Definition of the error that is to be reported– Added to section 6.6.

• “Not Used” command code– Error code to send when a “Not Used” command code is received has

been added to section 6.9.• Conformance statements added to section 6.10.• Referenced to conformance statements added to section 6-7, Partial

Implementation of RMAP• Informative annex (section 6.11) added providing possible

implementations of the RMAP CRC in VHDL and C-code.• Minor editorial changes.

Section 6.1 General

• Purpose– Provide a means of

• Writing to• Reading from• Registers or memory on a SpaceWire node• Over a SpaceWire network• Registers are considered to be memory mapped

– Be simple and effective– Flexible to encompass diverse applications

• RMAP Operations– Introduction to

• Write• Read• Read-Modify-Write

• Guide to Clause 6

SpaceWire Protocol Identifier

LogicalAddress

ProtocolID

Logical Address with Protocol ID

Rest of Packet EOP

LogicalAddress

ProtocolID

PathAddress

Path Address with Protocol ID

Rest of Packet EOP

RMAP Commands

• Write– With or without acknowledgement– Verifying data before writing or writing without verification

• Read• Read-Modify-Write

Write Commands

• Write non-acknowledged, non-verified– Writes zero or more bytes to memory in a destination node– Command header is checked using a CRC before the data is

written– Data is not checked before it is written– No acknowledgement given to indicate that the command has

been successfully executed

• Used for writing large amounts of data to a destination– Where it can be safely assumed that– The write operation completed successfully– Or that is not critical if it does not succeed– E.g. writing camera images to a temporary working buffer

Write Commands

• Write non-acknowledged, verified– Writes zero or more bytes to memory in a destination node– Command and data are both checked using CRCs before the data is

written– Limits the amount of data that can be transferred in a single write

operation – Owing to limited buffer space in destination– Erroneous data cannot be written to memory– No acknowledgement given to indicate that the command has been

successfully executed• Used for writing command registers and small amounts of data to a

destination– where it can be safely assumed that– the write operation completed successfully– or where errors are detected in a different way– E.g. writing many commands to different configuration registers in a

device and then checking for an error using a status register

Write Commands

• Write acknowledged, non-verified– Writes zero or more bytes to memory in a destination node– Command is checked using a CRC before the data is written– Data is not checked before it is written– Acknowledgement sent to indicate that the command has been

successfully executed

• used for writing large amounts of data to a destination– where it can be safely assumed that– the write operation completed successfully,– but an acknowledgement is required.– For example writing sensor data to memory.

Write Commands

• Write acknowledged, verified– Writes zero or more bytes to memory in a destination node– Command and data are both checked using CRCs before the

data is written– Limits the amount of data that can be transferred in a single write

operation – Owing to limited buffer space in destination– Erroneous data cannot be written to memory– Acknowledgement sent to indicate that the command has been

successfully executed

• Used for writing small amounts of data to a destination– where it is important to have confirmation that– the write operation was executed successfully.– For example writing to command or configuration registers.

Definitions

• Path address– Route to a node– Specifies output port to use for each router– Leading path address byte deleted after use by router

• Logical address– Identity of node– If unknown then default of 254 may be used– Node may accept or reject packets with logical address 254

• Destination path address– Path address to destination

• Destination logical address– Logical address of destination

Definitions

• Source path address– Path address back to source– Used to send ack or data back to source– Not needed if logical addressing being used– Leading zeros are ignored– To send to port zero all bytes should be set to zero

• Source logical address– Logical address to which destination node is to reply– Normally source address of node that sent the command– May be set to 254 (default) if command source does not have a

logical address

• Protocol Identifier– 01h for RMAP

Definitions

• Packet Type, Command, Source Address Length– Type of packet

• Command• Reply or acknowledgement

– Command• Read/Write/RMW• Verify / Don’t Verify• Acknowledge / Don’t Acknowledge• Increment Address / Don’t Increment

– Source Path Address Length• Number of four byte words containing the source path address• 0 means there is no source path address• Maximum of 3 words – 12 source path address bytes

Definitions

• Transaction identifier– Two bytes used to identify

• Command• Response or acknowledge

– That make up a transaction– Transaction ID sent in command is returned in reply/ack– Can be used back in source to associate reply/ack with the

command that caused it

Definitions

• Extended Address– 1-byte– Extends 32-bit memory address– Differentiates between various address spaces in destination

• Memory bank• Mailboxes• Register bank

• Memory Address– 4-bytes, 32-bit memory address– Used to determine what memory location a command is to

access– Registers and mailboxes are assumed to be memory mapped

Definitions

• Data length– Amount of data to be written or read in bytes

• Header CRC– 8-bit CRC – Used to confirm header is ok before executing command

• Data– Data to be written in a write command– Data read by a read command

• Data CRC– 8-bit CRC– Used to confirm that data is correct before being written in a verified

write command– Also confirms that data in non-verified write command was transferred

corectly (within limits of 8-bit CRC)• EOP

– SpaceWire End of Packet marker

6.3.1 Write Command

Destination Logical Address Protocol Identifier Packet Type, Command,Source Path Addr Len Destination Key

Source Logical Address Transaction Identifier Transaction Identifier Extended Write Address

Write Address (MS) Write Address Write Address Write Address (LS)

Data Length (MS) Data Length Data Length (LS) Header CRC

Data Data Data Data

Data Data CRC EOP

First byte transmitted

Last byte transmitted

Write = 1 Verify data(1)No Verify (0)

Command = 1

Increment/No inc. addr

Ack (1)/No ack (0)

Reserved= 0

Source PathAddress Length

Bits in Packet Type / Command / Source Path Address Length Byte

MSB LSB

Packet Type Command Source Path Address Length

Logical Addressing

6.3.2 Write Reply

Source Logical Address Protocol Identifier Packet Type, Command,Source Path Addr Len Status

Destination Logical Address Transaction Identifier Transaction Identifier Reply CRC

Write = 1 Verify data (1)No Verify (0)

Response= 0

Increment/No inc. addrAck = 1Reserved

Packet Type Command

Source Path Address Length

6.3.3 Write Command

Destination Path Address

Destination Logical Address Protocol Identifier Packet Type, Command,Source Path Addr Len Destination Key

Source Path Address Source Path Address Source Path Address Source Path Address

Source Logical Address Transaction Identifier Transaction Identifier Extended Write Address

Write Address (MS) Write Address Write Address Write Address (LS)

Data Data Data Data

Destination Path Address Destination Path Address

Data Data Data Data

Data Data CRC EOP

Write = 1 Verify data(1)No Verify (0)

Command = 1

Ack (1)/No ack (0)

Reserved= 0

MSB LSB

Packet Type Command Source Path Address Length

Path Addressing

6.3.4 Write Reply

Source Path Address

Destination Logical Address Transaction Identifier Transaction Identifier Reply CRC

Source Path Address Source Path Address

Write = 1 Verify data (1)No Verify (0)

Response= 0

Increment/No inc. addrAck = 1Reserved

Packet Type Command

6.3.5 Write Action

Write Request

Write DataRequest

WriteCommand

WriteReply

Write CompleteConfirmation

RMAPSource

RMAPDestination

Write DataAuthorisation

Write Data

Write DataIndication

USERAPPLICATION

SpaceWireNetwork

6.3.6 Write ErrorsWrite Command Header Error

Write Request

Source Destination

RecordPacketError

WriteCommand

Write Authorisation Rejection

Write Request

Write DataRequest

WriteCommand

Write ReplyError

AuthorisationFailure

Source Destination

Write DataAuthorisationRejection

Command Authorisation

• Destination user application• Can refuse to authorise command for any reason• E.g.

– Write address not 32-bit aligned– Length not a multiple of four bytes– Address range falls partially or completely outside an acceptable

region

Write Data Error

Write Request

Write DataError Indication

WriteCommandHeader

Write DataError Reply

Write DataFailure

Source Destination

RecordData Error

Write DataRequestWrite DataAuthorisation

WriteCommandData

Write Reply Error

Write RequestWriteCommand

Source Destination

WriteReply

RecordPacketError

Write DataRequestWrite DataAuthorisation

Write Data

6.3.7 Write Command Parameters

• Write Request parameters:– Destination address– Source address– Transaction identifier– Destination key– Write command options– Write address– Data length– Data

6.4 Read Command

• Read command– Reads one or more bytes of data– From specified area of memory in a destination node– Data read is returned in a reply packet.

6.4.1 Read Command

Read Address (MS) Read Address Read Address Read Address (LS)

Destination Logical Address Protocol Identifier Packet Type, CommandSource Path Addr Len Destination Key

Source Logical Address Transaction Identifier (MS) Transaction Identifier (LS) Extended Read Address

Read = 0 Read = 0Command= 1

Read = 1(Ack/No_Ack)

Reserved= 0

Packet Type Command

Logical address

6.4.2 Read Reply

Destination Logical AddressTransaction Identifier (MS) Transaction Identifier (LS) Reserved = 0

Data Data Data Data

Data Data CRC EOP

Read = 0 Read = 0Response= 0

Increment/No inc. addrRead = 1Reserved

Bits in Packet Type / Command / Source Address Path Length Byte

Packet Type Command

Logical address

6.4.3 Read Command

Read Address (MS) Read Address Read Address Read Address (LS)

Source Logical Address Transaction Identifier (MS) Transaction Identifier (LS) Extended Read Address

Read = 0 Read = 0Command= 1

Read = 1(Ack/No_Ack)

Reserved= 0

Packet Type Command

6.4.4 Read Reply

Source Path Address

Destination Logical AddressTransaction Identifier (MS) Transaction Identifier (LS) Reserved = 0

Data Data Data Data

Data Data CRC EOP

Read = 0 Read = 0Response= 0

Increment/No inc. addrRead = 1Reserved

Packet Type Command

6.4.5 Read Action

Read Request

Read DataRequest

ReadCommand

ReadReply

Read DataConfirmation

Source Destination

Read DataResponse

6.4.6 Read ErrorsRead Command Error

Read RequestReadCommand

Source Destination

RecordPacket Error

Read Authorisation Rejection

Read Request

Read DataRequest

ReadCommand

ReadReplyAuthorisationError

Source Destination

ReadAuthorisationRejection

Read Reply Header Error

Read Request

Read DataIndication

ReadCommand

ReadReply

Source Destination

Read DataResponse

RecordPacketError

Read Reply Data Error

Read Request

Read DataIndication

ReadCommand

ReadReply

Read DataFailure

Source Destination

Read DataResponse

6.4.7 Read Command Parameters

• Read Request parameters:– Destination address– Source address– Transaction identifier– Destination key– Read command options– Read address– Data length

6.5 Read-Modify-Write Command

• Read-modify-write command– Reads a register (or memory)– Returns its value– Writes a new value, specified in the command, to the register.– Mask can be included, in the command– So that only certain bits of the register are written

• Provides an atomic operation that can be used for semaphores and other handshaking operations.

Example Read-Modify-Write Operation

1 0 0 0 1 0 0 0

1 0 0 0 1 1 1 0

1 1 1 0 0 0 1 1

Data in command (Data)

Mask in command (Mask)

Data read from destination memory and returned to source (Read)

1 1 1 0 1 0 0 1 Data written to destination memory= (Mask AND Data) OR (/Mask.Read)

6.5.1 Read-Modify-Write Command

Source Logical Address Transaction Identifier Transaction Identifier Extended RMW Address

RMW Address (MS) RMW Address RMW Address RMW Address (LS)

Data +Mask Length (MS)= 00h

Data + Mask Length= 00h

Data + Mask Length (LS)= 00h, 02h, 04h, 06h or 08h Header CRC

Data (MS) Data Data Data (LS)

Data/Mask CRC EOP

Read = 0 Verify DataBefore WR = 1Command = 1 Incr. address

= 1Ack/No_Ack

= 1Reserved = 0

Packet Type Command

Mask (MS) Mask Mask Mask (LS)

Logical Address

6.5.2 Read-Modify-Write Reply

Destination Logical Address Transaction Identifier (MS) Transaction Identifier (LS) Reserved = 0

Data Length (MS) = 0 Data Length = 0 Data Length (LS)= 01h, 02h, 03h or 04h Header CRC

Data Data Data Data

Data CRC EOP

Read = 0 Verify DataBefore WR = 1Response = 0 Inc. address

= 1Ack/No_Ack

= 1Reserved = 0

Packet Type Command

Logical Address

6.5.3 Read-Modify-Write Command

Source Logical Address Transaction Identifier Transaction Identifier Extended RMW Address

RMW Address (MS) RMW Address RMW Address RMW Address (LS)

Data +Mask Length (MS)= 00h

Data + Mask Length= 00h

Data + Mask Length (LS)= 00h, 02h, 04h, 06h or 08h Header CRC

Data (MS) Data Data Data (LS)

Data/Mask CRC EOP

Read = 0 Verify DataBefore WR = 1Command = 1 Incr. address

= 1Ack/No_Ack

= 1Reserved = 0

Packet Type Command

Mask (MS) Mask Mask Mask (LS)

6.5.4 Read-Modify-Write Reply

Source Path Address

Destination Logical Address Transaction Identifier (MS) Transaction Identifier (LS) Reserved = 0

Data Length (MS) = 0 Data Length = 0 Data Length (LS)= 01h, 02h, 03h or 04h Header CRC

Data Data Data Data

Data CRC EOP

Read = 0 Verify DataBefore WR = 1Response = 0 Inc. address

= 1Ack/No_Ack

= 1Reserved = 0

Packet Type Command

6.5.5 Read-Modify-Write Operation

RMW Request

RMW DataRequest

RMWCommand

RMWReply

RMW CompleteConfirmation

Source Destination

Data Read and WriteAuthorisation

Write Data

6.5.6 Write ErrorsRMW Command Header Error

RMW Request

Source Destination

RecordPacketError

RMWCommand

RMW Authorisation Rejection

RMW Request

RMW DataRequest

RMWCommand

RMW ReplyError

Source Destination

RMW DataAuthorisationRejection

RMW Data Error

RMW Request

RMW DataError Indication

RMWCommandHeader

RMW DataError Reply

RMW DataFailure

Source Destination

RecordData Error

RMW DataRequestRMWAuthorisation

RMWCommandData

RMW Reply Error

RMW RequestRMWCommand

Source Destination

RMWReply

RecordPacketError

RMW DataRequestRMW DataAuthorisation

RMW Data

RMW DataIndication

6.5.7 RMW Command Parameters

• RMW Request parameters:– Destination address– Source address– Transaction identifier– Destination key– RMW command options– Memory address– Data length– Data– Mask

6.6 Error Codes

The header CRC was decoded correctly but the device key did not match that expected by the destination user application.

Invalid destination key 3

The header CRC was decoded correctly but the command byte is not accepted by the node or the command is not defined by the RMAP protocol.

RMAP command not supported by node

The detected error does not fit into the other error cases or the node does not support further distinction between the errors

General error code1

Command executed successfully

Error DescriptionErrorError Code

6.6 Error Codes

EEP marker detected before the end of the data. Indicates that there was a communication failure of some sort on the network.

Early EEP7

EOP marker detected beyond the expected end of the data.

Cargo larger than expected

Late EOP

Cargo too large

EOP marker detected before the end of the data.

Early EOP5

Error in the CRC of the data fieldInvalid data CRC4

6.6 Error Codes

The verify before write bit of the command was set so that the data field was buffered in order verify the data CRC before transferring the data to destination memory. The data field was longer than could fit inside the verify buffer resulting in a buffer overrun.Note the command will not be executed in this case.

Verify buffer overrun9

EEP marker detected beyond the expected end of the data. Indicates that there was a communication failure of some sort on the network.

Late EEP

DELETE Reserved

6.6 Error Codes

The header CRC was decoded correctly but the destination logical address was not the value expected by the destination.

Invalid destination logical address

The data in a RMW command does not match the data length field or is invalid (01h, 03h, 05h, 07h or >08h).

RMW data length error11

The destination user application did not authorise the requested operation

Authorisation failure10

Partial Implementation of RMAP

• Partial implementations are permitted• For example:

– Support of write and read but not RMW commands– Support of 32-bit data lengths only

• If destination receives command it does not support• Or command with options not supported• It refuses to authorise the command• Command is not executed• If reply requested then it will contain Authorisation

Failure error code

6.8 RMAP Use Cases6.8.1 Write to Memory

SpaceWireInterface

RMAPInterface

DMA Controller Memory

MemPtr = 001000h

DataCtr = 000010hData

SpaceWire

SpaceWire-RMAP Interface Destination Application

6.8.2 Read from Memory

SpaceWireInterface

RMAP Interface

HostProcessor

MemoryMem Addr RegSpaceWire

SpaceWire-RMAP Interface Destination Application

Data Len Reg

Data FIFO

Dest Key Reg

ProcessorBus

Status Reg

RMAP Use Cases

• Reading and Writing to Registers• Write to FIFO• Read from FIFO• Write to Mailbox• Read from Mailbox• Repeating Transaction ID

– Can prevent information being written twice to a FIFO or command register

6.9 RMAP Command Summary

• Table of command fields added in section 6.9• Details the set of valid commands• And command codes that are not used.

6.10 RMAP Conformance

• Conformance statements• Several SpaceWire RMAP compatible subsets can be

identified each of which implements only a part of the SpaceWire RMAP standard:– RMAP Write Command– RMAP Read Command– RMAP Read-Modify-Write Command

6.10.2.1 RMAP Write Command

Error Codes6.6

Write Command6.3

Protocol Identifier5

TitleRelevant clauses or subclauses

Write Command Equipment Characteristics

Incrementing address onlyAddress incrementation

0x00 0000 0000 – 0x00 0000 001CAccepted address ranges

0x20 Accepted destination keys

0xFE at power-on0x42 after initialisation

Accepted logical addresses32-bit word alignedWord or byte addressBig EndianEndianess

No4SVerified write--NS64-bit write

No8S32-bit write--NS16-bit write--NS8-bit write

Non-aligned access accepted

Maximum number of bytes allowed

Supported/Not Supported

ActionWrite Command

6.10.2.2 RMAP Read Command

Error Codes6.6

Read Command6.4

Read Command Equipment Characteristics

0x00 0000 0000 – 0x00 0000 001C0x00 0000 0020 – 0x00 0000 003C

Accepted address ranges

Accepted logical addresses

32-bit word alignedWord or byte address

Big EndianEndianess

--NS64-bit read

No8S32-bit read

--NS16-bit read

--NS8-bit read

Action

Read Command

6.10.2.3 RMAP RMW Command

Error Codes6.6

Read-Modify-Write Command6.5

RMW Command Equipment Characteristics

0x00 0000 0000 – 0x00 0000 001CAccepted address ranges

Accepted logical addresses32-bit word alignedWord or byte addressBig EndianEndianess

--NS64-bit read-modify-write

No4S32-bit read-modify-write

--NS16-bit read-modify-write--NS8-bit read-modify-write

ActionRead-Modify-Write Command

6.11 CRC Implementation

• Header CRC– 8-bit CRC– Fairly simple to compute– Provides reasonable protection for short header

• Data CRC– Same 8-bit CRC– May be computed using same hardware/software as Header CRC– Provides reasonable protection for short data lengths– For long packets of data additional protection may be necessary– Which must be supplied by the user application

• Galois version of CRC used– X8 + X2 + X1 + 1– Initialised with zero– Simple to implement in hardware

• VHDL and C-code included

Comments from Torbjorn Holt

RMAP Demonstration

HostPC

SpaceWireUSB Brick

SpaceWireRouter

RMAPSoftware

RMAPHardware

RMAP Demonstration

HostPC

SpaceWireUSB Brick

Link Analyser

SpaceWireRouter

RMAPSoftware

RMAPHardware

RMAP Command

• Header 00– Configuration port of Router

• FE 01 4D 20– FE = Destination logical address (default)– 01 = RMAP Protocol ID– 4D = Read command, Source path length = 1– 20 = Destination key (default destination key for router)

• 00 00 00 03– Source path address– Leading zeros ignored– 3 is the source path address– Router returns configuration information on port that it received

command– 3 is the USB port of the Brick

RMAP Command (Continued)

• FE 00 A6 00– FE = Source logical address (default)– 00 A6 = Transaction ID– 00 = Extended address

• 00 00 00 01– Read memory address

• 00 00 04 48– 00 00 04 = Data length– 48 = Header CRC

RMAP Response

• Header 03– Path address to Brick USB port

• FE 01 0D 00– FE = Source logical address (default)– 01 = RMAP Protocol ID– 0D = Read Response– 00 = Status (success)

• FE 00 A6 00– FE = Destination logical address (default)– 00 A6 = Transaction ID– 00 = Reserved

RMAP Response (Continued)

• 00 00 04 D0– 00 00 04 = Data length (4 bytes)– D0 = Header CRC

• 00 01 81 11– 00 01 81 11 = Data read from Router (Network Discovery

Register)– 01 81 : bits set for links that are operational (USB, port 8, port 1)– 11 : return port is link 1, device is a router

• BF– Data CRC

spacewire rmap protocolspacewire.esa.int/wg/spacewire/spw-snp-wg-mtg5... · spacewire rmap protocol...

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